These operations, however, could not be carried far at that period; even Lovitz still adhered to the phlogiston-theory, and only at the beginning of the 19th century Petrov and others tried to prove its inconsistency. Still later, after the discoveries of Kirchhof and Hess in the domain of catalysis and thermo-chemistry, Russian chemists began to make further original investigations: in 1842 Sinin arrived by means of experiment at some organic bases of chemical processes and obtained very valuable results with regard to aniline. He founded a famous school of Russian chemists: one of these, Butlerov, established a new principle of "chemical constitution" of matter, and had in his turn pupils, who worked under his influence—Markovnikov and Saitsev; Beketov began his investigations also under the direction of Sinin and developed original views on the affinity of chemical elements and on thermo-chemistry. Some years after the principal discovery of Sinin was made, Mendeleyev, a most talented supporter of the theory of "chemical types," discovered the periodic law of elements, and Menshutkin founded a new centre of chemical inquiries.
Similar investigations in other branches of natural science developed during this period and were also made subsequently by foreign and Russian students, who began to state the laws which manifest themselves in different forms and processes of matter and life, and
ковскимъ Университетомъ, М. 1912. Б. Меншуткинъ, Ломоносовъ, какъ естество и спытатель, С.-Пб. 1911 П. Вальденъ, Ломоносовъ, какъ химикъ, С.-Пб. 1911. В. Бернадскій, О зиаченіи трудовъ М. В. Ломоносова въ минералогіи и геологіи, М. 1900, etc.
